where to store numerical rating?

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Lets say I

supplies 4 different types of product (A,B,C,D)my main objective is to capture rating( 20 types) of these different types of product in alphabet and also in numerical thru lookup table

I created following tables

Supplier( supplierid, supplier)01� ABC02� DEF....

Suppliertype( suppliertypeid, supplierid, typesof products)01� 01� A02� 01� B03� 01� C04� 01� D05� 02� A ........

I created thirdtable

Ratingtable(departmentid,suppliertype,rating)

Dept� 01� AAADept� 02� AADept� 03� AAA

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Am i on right track and beside that I also have to put numerical value for rating, where is the best place to add column for numerical rating?Can i add rating and numerical value to suppliertype table and taking off rating from rating table?

There are 20 types of rating with numerical value ( in look up table)
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